The invention relates to a brake control system for motor vehicles, having an electronic control device, having a brake pedal via the actuation of which a braking intent is specifiable by the driver, having means for detecting the actuation of the brake pedal, and having secondary braking components which are controllable decoupled from the brake pedal for setting a brake pressure in the wheel brake cylinders.
A brake control system of this type is known from EP 0 867 350 B1, for example. This known brake control system has an electronic control device, a brake pedal via the actuation of which a braking intent, in the present case in the form of a pilot pressure value, is specifiable by the driver, and secondary braking components which are controllable decoupled from the brake pedal. The secondary braking components which are controllable decoupled from the brake pedal are in particular hydraulic components such as an ABS or ASC or DSC control loop, for example electrically controllable valves and pumps for conveying pressure means.
In conventional pedal-coupled brake control systems, during normal operation the pressure in the wheel brake cylinders is equal to the pilot pressure. By means of an auxiliary mode, the actual pressure in the wheel brake cylinders may be increased, and may be greater than the pilot pressure. The condition for switching over to the additional auxiliary mode may be triggered by various events. For example, the switchover may take place in an emergency braking mode having increased pressure requirements as the result of exceeding certain actuation thresholds. Similarly, other conditions may result in activation of an additional auxiliary mode.
For further technical background, reference is made to DE 10 2010 040 726 A1, relating to a brake control system for electric or hybrid vehicles having regenerative braking.
In these types of customary braking systems known heretofore, the functional relationship between the brake pedal travel or the brake pedal force and the pilot pressure or the pressure in the wheel brake cylinders is predetermined in the form of a so-called brake pedal characteristic.
The object of the invention is to optimize the brake control systems of the type mentioned at the outset with regard to the brake pedal characteristic.
This object is achieved by the features of claim 1. Advantageous refinements of the invention are the subject matter of the subclaims.
The invention is directed to a brake control system having an electronic control device, having a brake pedal via the actuation of which a braking intent in the form of a pedal travel and/or a pilot pressure and/or a pedal force is specifiable by the driver, and having secondary braking components which are controllable decoupled from the brake pedal for setting pressure values in the wheel brake cylinders of a motor vehicle wheel.
According to the invention, the brake pedal characteristic is variably specifiable as a function of defined conditions.
The invention is based on the following considerations:
Present brake boosters are generally based on a mechanical brake booster. The energy for the brake boosting is generated either by negative pressure or by means of hydraulic pressure. Other systems, for example electrohydraulic or electromechanical brake systems, utilize electrical energy for the brake boosting.
The brake pedal characteristic (the association of the pedal force or the pedal travel with the resulting brake pressure or with the vehicle deceleration), in particular of mechanical brake boosters, is subject to the selection of the mechanical components and the chosen settings. The boost factor and the level of overall assistance may be set for dimensioning the design. In the sensitive response range, the jump upon actuation of the brake pedal may be influenced by the interaction of the sensor plate and the reaction plate, but, at least for mechanical brake boosters, is always predetermined corresponding to the design.
Depending on the driving situation, however, it makes sense to have different brake pedal characteristics. Thus, in normal roadway driving (“on-road travel”), in particular in interaction with an automatic transmission, a design having a pronounced jump characteristic is perceived as pleasant. In addition, a relatively broad pressure hysteresis between the ascending characteristic curve and the descending characteristic curve is perceived as comfortable. However, in other situations, in particular during travel outside normal roadway driving (“off-road travel”), a different brake pedal characteristic without a distinct jump and having a narrower pressure hysteresis is perceived as more pleasant.
Brake pedal actuations which are decoupled from the wheel brake via the actuators (secondary brake circuit components) for the pressure build-up, depending on the application (hydraulic, electrohydraulic, or electromechanical braking system), present the option for providing different curves of the brake pedal characteristic.
The driver's intent (desired braking power or desired vehicle deceleration) may be interpreted via the sensor system (for example, for measuring the brake pedal travel and/or the brake pedal force) at the pedal travel simulator. Either on-road travel or off-road travel in particular or some other driving situation is automatically recognized by an evaluation module internal to the control device, based on the detection of vehicle state or vehicle surroundings parameters, or the driver has the option for manually switching over between various brake pedal characteristics, using a certain control element. The appropriate brake pedal characteristic may thus be implemented corresponding to the driving situation.
One exemplary embodiment of the invention is illustrated in the drawings, which show the following:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.